Automatic tuning mechanism



' Feb. 1; 1944. LE ROY J. LEiSHMAN 2,340,393

AUTOMATIC TUNING MECHANISM Filed May 13, 1940 3 Sheets-Sheet l III/l.II/III- I 11/1.

iNVEN 'roP Feb. 1, 1944. LE ROY J. LEISHMAN 2,340,393

AUTOMATIC TUNING MECHANISM Filed May 15, 1940 3 Sheets-Sheet 2 INVENTOIL1944- LE ROY J. LEISHMAN 2,340,393

AUTOMAT I C TUNING MECHANI SM Filed May 13, 1940 3 Sheets-Sheet 3 pm: hM

INVENTOKJ Patented Feb. 1, 1944 UNITED STATES PATENT OFFICE AUTOMATICTUNING MECHANISM Le Roy J. Leishman, Los Angelcs, Calif. Application May13, 1940, Serial No. 334,685

8 Claims.

My invention. as described herein. relates to antomatic tuningmechanisms, including devices of this class used in radio receivers, andmore particulariy to that type of automatic tuning apparatus in whichthe movable control of the resonance-varying device is urged in onedirection by a loading spring and moved predetermined distances in theopposite direction by means of individually operable selectors. and inwhich an adjusting means for preselecting the position in which thecontrol will come to rest is provided for each selector. Tuners of thisgeneral class are exemplified by the devices of th following designatedpatents: Marvin, No. 1,704,754; Faas. No. 1,928,200; Bast, No.1,687,420; and British Patent No. 405,716, issued to Freytag et al.

y invention may be used with any type of resonance-varying apparatushaving a. movable control, including variable condensers, but it isespecially adaptable for variable permeability tuning.

None of the embodiments shown in the above identified patents have comeinto use in the United States because of complicated construction,inconvenient operation, inaccurate tuning. or some combination of two orall of these defects, nor are any of these tuners well suited for usewith variable permeability tuning, in which the actual control membermoves in a straight line.

Because of the latching means, however, tuners of the general class ofthe Marvin and Freytag structures are ideal for adaptations in which itis desirable for the operating button to remain depressed as a means ofindicating the station to which the set is tuned, or for use in setsthat must be used under conditions in which vibration is apt to jar thecontrol from its adjusted position, as in an automobile receiver.

It is one of the objects of the present invention to remove the defectsthat have been inherent in past devices of the spring-loaded variety inorder to realize the full benefits of the desirable features just setforth.

More specifically. as far as these objectives are concerned, the presentinvention aims to increase accuracy by reducing the number of partsinterposed between the adjustable position-determining means associatedwith each selector and the movable control that must be accuratelypositioned for proper tuning; to provide means for removing play fromthe mechanism; to produce a device that will be sturdy and dependable;and to make easy operation possible.

Only one of the patents mentioned discloses a. tuner that can be setfrom the button, but the structure is too complicated and costly forreceivers that are low enough in price for the average purchaser. It istherefore an object of the present invention to simplify the button ad-Justin-g arrangement.

Another object is to make it possible for all the buttons to be inalignment in their rest positions regardless of the adjustment of theassociated adjusting means without resorting to complex or unnecessarilycostly expedients to attain this result.

In the device for the Freytag patent, any one of the buttons may be usedas a manual knob for tuning the receiver through its entire rang offrequencies. The pressing of any other button for returning the tuningcontrol to a predetermined position will automatically declutch theplunger being used for manual tuning, and such manual knob regardless ofits high ratio therefore does not increase the button pressure. Thestructure of the Freytag button and plunger. however, is unnecessarilycomplicated for this purpose, and the present invention therefore aimsto simplify the construction and reduce the number of required parts.

Another object of my invention is to provide means in certain of theembodiments for removing play between the threads of the adjusting screwand the screw-threaded parts of the supporting member, and to do this inan inexpensive manner.

Another object is the reduction of the button pressure required tooperate the device.

Further objects of my invention are to reduce the torque of the dial orindicating means, and to make it possible to have a relatively longpointer travel without gears or a large driving pulley.

At the present time, the cores of permeability tuners must moveapproximately 1% inch to cover the entire broadcast band if the tuningis not to be too critical. The button stroke. however, should not bemore than half of this core travel, as buttons that protrude very farfrom the panel of the set are unsightly. It is desirable to have theshortest possible button stroke consistent with reasonable buttonpressure. It is therefore an important object of my invention to providesimple, cheap and eillcient motion-multiplying means for stepping up theshort button stroke sufiiciently to move the core through its requiredrange of travel.

Additional objects will appear as the specification proceeds.

In the accompanying drawings:

Fig. 1 is a section taken on line i-i of Fig. 2, showing one form of myinvention.

Fig. 2 is a top plan view, partly in section. of the device shown inFig. 1.

Fig. 3 is a section taken on line 3-3 of Fig. 1, showing the guidingmeans for keeping the racks in mesh.

Fig. 4 is a section taken on line 4-4 of Fig. 5. and shows anothermodification of my invention.

Fig. 5 is a top plan view. partly in section, of the embodiment shown inFig. 4.

Fig, 6 is an isometric view of the motion-multiplying means and coremounting rack of the embodiment illustrated also in Figs. 4 and 5.

Fig. 7, on the first page of the drawings. illustrates a variant of thedevice of Figs. 8, 9 and 10, and corresponds to the sectional views ofFigs. 1 and 4.

Fig. 8 illustrates the form of the invention that I prefer, and is asection taken on line B-8 of Fig. 10.

Fig. 9 is a front elevation, partly in section, of the device shown inFigs. 8 and 10.

Fig. 10 is a top plan view of the embodiment illustrated in Figs. 8 and9.

Fig. 11 is a cross section of the manual knob and associated parts.showing the means for keeping the knob in the same longitudinal positionwith respect to the plunger assembly regardless of the relativelongitudinal position of its adjusting screw.

Fig. 12 is a sectional view of a modification of the button structureshown in Fig. 8.

Fig. 13 illustrates one method of removing play between the threads ofthe screw and the associated screw-threaded portions of the plunger.

Fig. 14 illustrates another method of removing play between the threadsso that the screw will fit snugly in its bearings and resist accidentalturning.

In the embodiment of my invention shown in Figs. 1, 2 and 3. themechanism is supported by a frame consisting of side plates Fl and F2and front and back plates F3 and F4. respectively. A shaft S isJournaled in the side plates Fl and F2. Rigidly attached to this are twosmall gears GI and G2, each located at one end and adjoining the innersurface of the end plates. Two larger gears. of identical size, arerigidly mounted on shaft 8 next to the small gears GI and (32. One ofthese large gears. G3, is shown in Figs. 1, 2 and 3. but its mate isconcealed beneath rack R4 in Fig. 2.

A U-shaped carriage, comprising parallel racks RI and R2. has a frontportion Yl yoklng the side racks RI and R2, which mesh respectively withthe small gears GI and G2. Each of these racks is provided with twooutwardly extending lugs, preferably sheared and formed from the stock.and these lugs slide in slots in the end plates to support the racks andkeep the teeth in mesh. Lugs It and 12 are shown in dotted lines in Fig.1, sliding in slot Al in end plate Fl. Another view of lug It appears inFig. 3.

A similar U-shaped member, disposed with the teeth at the bottom.comprises racks R3 and R4, and a connecting yoke portion Y2. Racks R3and R4 mesh with the two large gears. as indicated clearly in Figs. 1and 3, in which rack R3 is shown in mesh with gear G3. These racks areguided in a straight path by lugs 13 and II, as shown in Figs. 2 and 3.These lugs are shaped with a shoulder as shown in Fig. 3 to take up thespace between the racks and the end plates, but the same purpose may beserved by using 0. lug of the same width throughout and taking up thespace with washers.

The yoke Y2 supports a plurality of permeability cores C arranged tomove in and out of the tuning coils L. The art affords a variety of waysfor mounting the cores and coils, but none is shown in detail in any ofthe figures of the drawings. as such mounting means are not a part ofthis invention.

A series of plunger devices are mounted in the front and back plates F3and F4 for longitudinal movement, but as these are alike, a descriptionof one will serve for the group. Each plunger comprises a flat bar P.provided with front and rear motion-limiting shoulders E and D. alatching lug H, and a pair of lugs K in which is journaled an adjustingscrew M, having a flat or keyed end 2 on which is mounted button 0 whichhas a recess to fit the end 2 so that the turning of the button willrotate the screw. Each screw is provided with a collar or similar meansQ for preventing longitudinal movement of the screw, its longitudinalmovement in the other direction being prevented by the journal itself.Each screw carries a travelling nut N constrained against rotation by afiat side fitting against the adjacent side of bar P. The plungers areheld in operative positions against bumper V by retainlng springs Ji,J2, J3 and J4.

A latch bar T is journalled in the side plates Fl and F2 by means ofintegral lugs U, and held against the plungers by springs J5 and J5.attached to the latch bar and the side plates.

Two loading springs J1 and J8 pull the upper U -shaped member back, and,through the medium of the gears, force the lower U-shaped member towardthe front of the mechanism.

When any plunger is pressed in, the lug H passes over the end of latchbar T, and is locked in operated position by means of the latch bar. theend of which is held behind the shoulder of the lug by means of springsJ5 and JG. The travelling or position-determining nut, N2 on thedepressed plunger of Figs. 1 and 2, receives the outward thrust of yokeor abutment Yi, and by its adjustment determines the position of bothcarriages, which, in turn, determine how far the cores are positionedinside the tuning coils.

When another plunger is pressed in, its rounded or cammed shoulder Hmoves the latch bar to release the previously locked plunger, and thetravelling nut of the newly depressed plunger now acts to position thecores through the instrumentalit of the racks and gears.

It will be evident that the turning of the button on any depressedplunger will move the position-determining nut along the screw and that,since the depressed plunger is latched in operated position, the nutwill move the lower carriage backward or forward. inasmuch as abutmentY! is constantly urged forward under action of the loading springs.

From the foregoing description it will be clear that the operation ofany button will position the cores and tune the set according to theprevious adjustment of the position-determining nut.

No manual tuning means is shown in the figures for this species, nor inFigs. 4. 5 and 6 for the species that they illustrate, because suchmanual tuning means is illustrated in detail in Figs. 8. 9 and 10 anddescribed in following parts of this specification. However, allembodiments require some provision for manual tuning, and

it may be assumed that the forms oi my invention for which no manualarrangement is shown in the figures, are nevertheless provided with somesuch means, either of a type old in the art or of the form illustratedin Figs. 8. 9 and 10 and described in connection therewith.

An important feature of my invention resides in the interposition ofmotion-multiplying means between the plungers and the cores, whereby theshort stroke of the plungers controls the longer stroke of the cores. Inthe embodiment just described, such means is provided by the carriages.gears and the shaft.

The species illustrated in Figs. 4. 5 and 6 cmploys an entirelydifferent motion-multiplying arrangement than that in the species justdescribed. As the operation and most of the features of thismodification are essentially the same as in the embodiment of Figs. 1. 2and 3. none of the substantially identical parts will be described. andthe description oi this species will be confined to the elements thatare different.

Links Gi and G2 are pivoted by means of studs or bolts WI and W2respectively on side plates Fl and F2 respectively. These links arerigidly connected by rod Yl. Links Gi and G3 are rotatably connected bypin BI, and the corresponding links on the other side of themotionmultiplying device are similarly connected by pin B2. The lower orfree ends of links G3 and G4 are provided with pins Zl and Z2respectively. each of which protrudes on both sides of the link. On theinner ends of these pins a bracket Y! is pivoted. The outer ends ofthese pins are constrained to move in a straight line by slots in whichthey move in the side plates. One such slot, A2, is shown in Fig. 4.Loading springs J1 and JB serve not only to pull bracket Y2 toward thefront of the tuner. but also. because of the position at which they areconnected, to keep the face of the main yoke portion in a verticalplane.

The cores C are connected to this yoke by any suitable means.

The position-determining means in this modification are shaped in themanner shown because they need to be reinforced on account of theirextra height, which is required to enable them to engage rod Yl in allits possible positions.

In this embodiment. bracket Y2 has more than twice the horizontal travelof rod Yi. and the difference can be made even greater by attaching rodYl nearer to the pivots of links GI and G2. If the ratio of travel mustbe very great, additional links may be interposed between links GI andG3. and between G2 and G4. with all the lower connecting pins of thelinks in each train moving in a slot.

In the device of Fig. 'l. the coils are mounted at the top. and bracketY2, carrying the cores, is constrained to move in a straight line by thepins that move in the slots in the side plates. The figure shows onesuch pin, Zl. moving in slot C. Link G3 serves in this embodiment not aspart of the motion-multiplying means. but to convert the arcuate motionof pivoted link G I, to which it is rotatably attached, into therectilinear motion required by bracket Y2. Corresponding links, notshown in the figure. are of course used on the other side of the device;and rod Yi. shown connected to link GI, is connected at the other end toa corresponding link to form a motion-multiplying means consisting of asingle integral assembly which moves as a unit.

The remaining parts of this embodiment are substantially the same andfunction the same as the corresponding parts in the form previouslydescribed which bear the same reference characters.

In the device of Figs. 8, 9 and 10, the integral pivoted structure ofFig. 7. which comprises three rigidly connected parts. is replaced by aone piece member G which functions the same and multiplies the motionimparted by the pioneers in the same way. This part. however. may bestamped and formed. A pulley segment I is attached to bar G at one endthereof. and the entire structure is pivoted on the end plates Fl andF2. The link (33 of Fig. '1 is replaced by a flexible wire, which method0! connecting a core to a rotatable member is not original with me.

The plunger structure shown in Figs. 8 to 14 inclusive embodiesimportant improvements and simplifications over the prior art.

The position-determining means proper consists of a single rod or screwM with threads that engage in corresponding threads in the holes in lugsK through which the rod is threaded. If these holes are tapped in theconventional way in a single operation with a single tap and if neitherthe bar P nor the lugs are distorted in any manner. screw M will fit soloosely in the lugs that it will not maintain its adjustment. This maybe prevented to some degree by providing no clearance between the maleand female threads. but Figs. 13 and 14 illustrate a simple preferredmeth- 0d. The lugs may be threaded with the bar very slightly distortedas shown in exaggerated form in broken lines in Fig. 14. and when thebar assumes its normal shape after the threading operation. the threadsof one lug are displaced with relation to the threads in the other lug.The amount of distortion may be controlled by a fixture so that thedistortion will not be so great that the screw will not engage thethreads in the second lug. but so that the screw will neverthelessencounter enough friction on the sides of the threads to keep the screwfrom turning when it is not rotated deliberately.

A similar result may be achieved by holding the lug in distortedposition during the tapping operation. as indicated in exaggerated formin dotted lines in Fig. 13, or both lugs may be tapped in their formedposition and at least one of them bent afterward to displace the threadssufficiently for the required result.

As shown in Fig. 8. the outer end 2 of the rod or screw is flat. but anyshape other than round with no interruptions in the curved peripherywill answer the purpose. A key-way or a single flat side will suffice.The term keyed portion" in the claims is intended to cover any of theseequivalent shapes. The button 0 shown in cross-section in Fig. 8 has alongitudinal recess enlarged at the open end to pass over the end of thethreaded portion of the screw in any of its adjusted positions, and therecess is shaped for the remainder of its depth to fit over the keyedend of the rod or screw in any of its longitudinal positions. When thebutton is turned to the right to adjust the screw inwardly. the externalend of the screw will move out of the button, which is prevented fromfollowing the screw by the abutmentor formed lug Kl on the plunger bar.When the button is turned in the opposite direction to adjust the screwoutwardly, the button will of course move away from lug Ki. but onaccount of the length of the recess. the button will move back againstlug K the first time the button is pressed to operate the plunger.

Fig. 12 shows a modification of the button and screw structure. In thisform, the outer lug Ki has a hole large enough to clear the keyed end ofthe rod or screw, and an extra lug K2 with a threaded hole is providedto afford the second threaded bearing required. The button of thisvariant may have a recess of uniform cross section throughout the lengthof the recess. The operation of this arrangement is the same as thatshown in Fig. 8.

In Figs. 8, 9, l0 and 11, a manual tuning knob is shown, which may alsobe used in any of the other embodiments. Such tuning knob must becapable of rotation in a direction to move the screw outwardly withoutmoving the button away from abutment or lug K. I have met theserequirements in a simple and inexpensive way. The keyed end 2 of screw Mcarries a keyed collar 4 which turns with the screw but which permitsthe screw to move longitudinally therethrough. In assembly, acompression spring J9 is placed over the keyed portion 2 after thecollar has been placed thereon, and a pin or other abutting means 5 isthen placed in position at the end of the screw. The knob 3 has alongitudlnal recess wide enough to clear the spring J9 and pin 5, but ofproper diameter or shape to fit the collar 4 to which it is secured bmeans of a set screw 6 or suitable keying means. Spring J9, pressing oncollar 4, keeps the end of the knob tight against abutment K under alloperating conditions.

In the embodiment shown in Figs. 8, 9 and 10. a single loading springdevice Jl, illustrated in spiral form, not only acts to urge the movableparts of the tuner each in one operative direction. but to operate theindicating device which is connected to the segment pulley i by a singlecord I. The particular part of the device to which cord 1 is attached,is the movable or floating pulley-support B, carrying the pulley 9. Oneend of a second cord Ill is attached to the frame at point i3 behind thescale II, as indicated in Fig. 9. It passes around pulley B and isattached at the other end to the spring-actuated reel or loading spring.11. This device may reel up the cord as a tape measure or flexiblesteel tape is wound into the case in numerous familiar devices that areon the market. An indicator Ii is attached to cord iil between thespring device and the pulley 9. The spring device acts to hold thisindicator at the left end of the scale l2 and to pull the floatingpulley 9 to a position about half way across the back of the scale. Aspulley l2 pulls on its supporting bracket 8, it pulls on cord 1, whichpasses over pulley l4 and pulls on the segment puley l to which it isconnected, tending to hold pivoted member G in its extreme forwardposition.

Motion-multiplying member G is moved in the opposite direction againstthe action of the loading spring J1 by the end of screws M, each plungeroperating to position member G and the connected cores C according tothe particular ad- Justment of its associated screw. The latching deviceT and the bumper V operate as in the devices of the preceding figures,and thus do not need description. The bumper V. in fact, is notessential, and is therefore omitted from some of the figuresillustrating the various forms of my device.

The forms of my invention that I have illustrated and described, are butillustrative embodiments, and many equivalents for the essentialelements will readily suggest themselves to those skilled in the art.Various rearrangements, ad-

ditions, substitutions and transpositions are also possible within thebroad scope of my invention: and the essential parts or theirequivalents may also, of course, be disposed to move in different planesand directions than those represented.

My claims are:

1. In a radio tuning mechanism, a combination including: a supportingframe comprising a front plate and a back plate; a rectilinearly movablecontrol for said mechanism; an operating device for said controldisposed between said plates: resilient means for actuating said deviceand moving said control in one direction: a plurality of plunger memberseach slidably mounted in both of said plates; a plurality of adjustableposltion-determining means each carried by one of said members andadapted to engage and actuate said device to move said control in theopposite direction, said position-determining means also comprising arotatable male screw extending substantially longitudinally of theassociated member, and means on the external end of said screw and freefrom engagement with either of said plates for imparting rectilinearmotion to said screw; and latching means common to all of said membersfor lockin any of said members in a fixed position.

2. In a radio tuning mechanism, a combination including:resonance-varying means; a movable control for said resonance-varyingmeans; a pair of relatively large gears connected to turn with equalangular velocity; a pair of relatively small gears each connected toturn as a unit with one of said large gears; a first carriage comprisinga pair of racks meshing with said large gears; means connecting saidfirst carriage and said control; a second carriage comprising a pair ofracks meshing with said small gears and including an abutment extendingtransverse to the direction of motion thereof; resilient means forurging said racks each in a single direction respectlvely: and aplurality of operating devices each comprising adjustable means forengaging said abutment and moving said racks against the action of saidresilient means to position said control.

3. In a radio tuning mechanism, a combination including: aresonance-varying means; a movable control for said resonance-varyingmeans; a pair of relatively large gears connected to turn with equalangular velocity; a pair of relatively small gears each connected toturn as a unit with one of said large gears; a first carriage comprisinga pair of racks meshing with said large gears; means connecting saidfirst carriage and said small gears and including an abutment extendingtransverse to the direction of motion thereof; resilient means forurging said racks each in a single direction respectively; a pluralityof operating devices each comprising adjustable means for engaging saidabutment and moving said racks against the action of said resilientmeans to position said control; and latching means for immobilizing anyof said devices to maintain said control in a stationary position.

4. In a control-positioning mechanism having a movable control elementand a plurality of selectors each comprising adjustable means foroperating said mechanism to move said control each to a preselectedposition, motion-multiplying means interposed between said selectors andsaid control and including: a pair of substantially identical linkagedevices each comprising a plurality of movably connected links one ofwhich is pivoted at a fixed point; a rod connecting one of the links inone pair with the corresponding link in the other pair; said rodarranged and disposed for engagement by the adjustable means of any ofsaid selectors; a pin near the end of the link in each pair that isfurthest from said fixed point; a guide for each of said pins toconstrain its movement in a straight line; a bracket movably connectedto said furthest link in each of said pairs; and means connecting saidbracket and said control.

5. In a radio tuning mechanism having a positlonable control, a plungerdevice including: a supporting element comprising an abutment; arotatable position-determining member carried by said supporting elementand extending on both sides of said abutment and having a keyed outerend and externally threaded portions engaging in correspondingscrew-threaded portions or said element; and a button member having aforward end adapted to engage said abutment and a recess extendinglongitudinally of said button member from the forward end thereof. atleast a portion of said recess keyed to fit the outer end of saidposition-determining member.

6. In a plunger device for positioning a springloaded control or a radiotuning mechanism, a combination including: a supporting elementcomprising an abutment; a rotatable controlengaging andposition-determining first member disposed longitudinally of saidelement and having a keyed outer end and external screwthreaded portionsextending on both sides of said abutment and engaging in correspondingscrewthreaded portions of said element; and a button member having alongitudinal recess shaped at its forward end to clear the threads ofsaid first member, at least a portion of the remainder of said recesscomprising a keyed portion adapted to receive the keyed end of saidfirst member.

'1. In a device for positioning a spring-loaded control of a radiotuning mechanism, a combination including: a supporting elementcomprising an abutment; a rotatable control-engaging andposition-determining first member disposed substantially longitudinallyof said element and having externally screw-threaded portions engagingin corresponding screw-threaded portions of said element and having akeyed portion at its outer end; a keyed collar slidably mounted on saidkeyed portion; abutting means near the outer end of said keyed portion;an operating member rigidly mounted on said collar and having a recessadapted to receive and permit the free longitudinal movement of saidkeyed portion and abutting means; and a compression spring surroundingsaid keyed portion between said collar and said abutting means andacting through said collar to urge the forward end of said operatingmember toward the abutment on said element regardless of thelongitudinal position of said first member.

8. In a radio tuning mechanism having a positionable control, a plungerdevice for positioning said control, said device including: adjustablemeans for determining the position that said control will occupy uponoperation of said plunger, said means comprising a rotatable adjustingscrew having a keyed portion, an operating member slidably keyed to saidportion whereby said screw may be rotated, and a spring for urging saidmember along said portion in one longitudinal direction.

LE ROY J. LEISHMAN.

